2. In facultative obligations, the culpable loss of the object which the debtor may deliver in the substitution before the substitution is effected does give rise to any liability on the part of such debtor. 3. In alternative obligation, the nullity of one of the objects does not invalidate of the obligation which is still in force with respect to those which have no defect. 4. The nullity of the principal object invalidates the obligation, even if the substitute object is valid. 5. In case of concurrence of two or more creditors or two or more debtors in one and the same obligation, the presumption is that the obligation is only joint. 6. It is incumbent upon the party alleging that the obligation is solidary in character to prove such fact with a preponderance of evidence. 7. In a joint obligation, each obligor answers the whole liability. 8. In a "joint and several" obligation, the relationship between the active and the passive subjects is so close that each of them must comply with or demand the fulfilment of the part obligation. 9. The well-entrenched rule is that solidary obligations cannot be inferred lightly. They must be positively and clearly expressed. 10. In case of breach of a joint indivisible obligation, it will never be converted into an indemnity for damages. 11. The obligation is deemed to be indivisible when it is to give definite things and those which are not susceptible of partial performance. 12. Indivisibility refers to the prestation that is not capable of partial performance. 13. Solidarity refers to the prestation. 14. Indivisibility exists even if there is only one debtor and one creditor. 15. Solidarity exists only if there are two or more debtors or two or more creditors